1. Field of the Invention
The present invention relates to touch panels including touch sensors and display portions.
2. Description of the Related Art
In recent years, display devices including touch sensors have attracted attention. The display devices including touch sensors are referred to as touch panels, touch screens, or the like (hereinafter simply referred to as touch panels). Examples of the types of touch sensors include a resistive type, an acoustic pulse recognition type, a surface acoustic wave type, an infrared light-blocking type, a capacitive type, an electromagnetic induction type, an image recognition type, and the like. These types have different operating principles. In any type of touch sensor, data can be input when an object to be detected is in contact with a display device.
A conventional touch sensor is formed over or below an EL layer including a light-emitting layer. In the case where a touch sensor is formed over an EL layer as in Reference 1, it is necessary to provide a protective film or a protective substrate over a display surface. Thus, even if any high-definition display device is manufactured, visibility decreases and image quality degrades. In contrast, in the case where a touch sensor is formed below an EL layer as in Reference 2, an image can be displayed at high definition; however, it is difficult to apply pressure to the touch sensor. Thus, the touch sensor has a problem of the decrease in accuracy.